1. Field of the Invention
This invention relates to data storage and, more particularly, to techniques for resynchronizing mirrored volumes in storage systems.
2. Description of the Related Art
Many business organizations and governmental entities rely upon applications that access large amounts of data, often exceeding a terabyte or more of data, for mission-critical applications. Often such data is stored on many different storage devices, which may be centrally located or distributed throughout an enterprise. Such storage devices may be heterogeneous in nature, including many different types of devices from many different manufacturers.
To provide for a degree of security against loss of critical data, for example due to hardware failure or a site-wide catastrophe such as a fire or natural disaster, copies of critical data may be stored at more than one site. For example, critical data may be stored on several volumes, where one volume is configured to mirror another. A mirror volume may be located at a different physical site from a volume at a primary site, which may provide a backup source of data in case of a failure at the primary site.
If a failure occurs during system operation, mirrored data volumes may not reflect the same data (i.e., may become inconsistent), for example if data is written to one mirrored volume but not another. In some cases, inconsistent mirrors may need to be resynchronized following a failure in order for applications to continue operating properly. However, resynchronization of mirrored volumes located at different sites may suffer from slow performance, for example if the communications path between sites is bandwidth-constrained.